In my findings I have found that minerals, rocks and gemstones are all similar. They have many things in common but they also have lots of differences. When you encounter rocks (any) all of them are solid, hard to break, they can feel cool to the touch. How much dirt do they have inside? That's one of the differences. Gemstones have usually no trace of dirt inside. Minerals have some but not too much.(JK) The compounds of them are different. Anything that doesn't have the normal compounds of a common rock is categorized by either a gemstone or a mineral (AKA metals). There are many things that scientists look for in a metal and a gem. They are examined under a microscope.(Hi)